Insight into the supramolecular organization of columnar assemblies with phototunable chirality

Abstract

New supramolecular associations with photoaddressable azobenzene units have been synthesized in order to better understand the structure of these complexes and their mesophases. The complexes are formed by a melamine core and three V-shaped acids and they exhibit columnar mesomorphism. The acids consist of two different arms, one derived from azobenzene and the other derived from phenyl benzoate. This design has allowed decreasing T_g values and also avoiding the tendency to crystallize, favouring regular and reproducible structures, together with the possibility of photoresponse. The mesomorphic properties of the complexes have been studied by POM, DSC and X-ray diffraction, showing Col_h or Col_r mesophases. CD activity of these materials in the mesophase (that reveals chiral structures) has been controlled by irradiation with CPL. XRD and AFM studies have been carried out to check the molecular organization in the films before and after CPL exposure, which confirmed that the mesophase retains its structure after switching the corresponding supramolecular chirality.